Since you can't really see the person in the smaller version of the photograph, I have included a larger panorama version as well. It really helps to show the majestic scale of the dunes when you have something of a recognizable size (like a person) in the picture. Who is that person? Do they know that I have their picture on the web?

There are rules about whether you can display (or sell) photographs with people in them. I don't have to have permission to display this person's picture on my web site for two reasons:

Public Place
Anytime your picture is taken in a public gathering place like a national park or a football stadium, the photographer does not have to get your permission to use your image. Imagine if every sports photographer had to get a "permission slip" from every single sports fan just to take pictures of the game! (In fact, if you look at the back of a ticket stub, you might find out that the fine print includes language that gives permission to take your picture.)

Not Recognizable
If your image is not readily identifiable as "you", then  as in the first case  no permission is required.

The image of the person in the photo shown above falls into both of these categories. On the other hand, if I had taken a recognizable picture of someone - even in a public place - then I think that common courtesy would have been for me to get the person's name.